The present invention is directed to a daisy type print wheel apparatus and more specifically to the technique of driving and stopping the print wheel.
A typical daisy wheel printer is shown in U.S. Pat. No. 3,954,163 where a servo system stops the print wheel at each printing position and allows a hammer to strike the printing element. However, feedback control or servo systems are relatively expensive.
Other more mechanical techniques of stopping the daisy type printing wheel momentarily while the hammer is striking the wheel are illustrated in three other patents. Herterich Pat. No. 3,677,386 drives the print wheel by a crown gear arrangement and when the hammer engages the tongue of the daisy type print wheel the crown gear is withdrawn from driving a relationship with the print wheel. In a German Pat. No. 1,461,514 OLS the print elements are on the periphery of a disk and there is some type of spring-like clutch element between a drive shaft and a print shaft in a complex mechanical arrangement. Here apparently the ribbon is pressed against the type wheel to produce an impression. Finally in Hugel U.S. Pat. No. 3,353,647 a light friction motor normally rotates the daisy type print wheel with the wheel being stopped by some type of mechanical interference relationship.
All of the above three devices are mechanically cumbersome and will not provide high speed and accurate placement of the typed characters.